Chemicals called perfluoroalkyl substances (PFASs) have been used for more than 60 years to make products more stain-resistant, waterproof or nonstick. They’re used in cookware to keep food from clinging to pots and pans. They’re incorporated into clothing, like raingear, to help repel stains and water, and used in furniture and carpeting to make them resistant to stains and liquids. PFASs are also used in fast food and other packaging to keep food from sticking.

There have been plenty of health concerns about PFASs as the chemicals have been linked to high cholesterol, effects on the immune system, hormone disruption, low infant birth rates, and even cancer, according to the Environmental Protection Agency (EPA). Now a new study suggests the chemicals may also make it tougher to keep off weight.

The study, published in the journal PLOS Medicine, found that higher levels of PFASs in the blood were associated with increased weight gain after dieting, particularly in women. The compounds are referred to as “obesogens” because they may upset normal metabolism and increase your risk for gaining weight the more you are exposed to them. The study found that people with higher concentrations of PFAS in their bodies also had a lower resting metabolic rate (RMR), meaning they burn fewer calories during normal daily activities.

“The potential endocrine-disrupting effects of PFASs have been demonstrated in animal studies, but whether PFASs may interfere with body weight regulation in humans is largely unknown,” Gang Liu, lead researcher for the study and research fellow in the department of nutrition at Harvard T.H. Chan School of Public Health, tells MNN.

“Obesity has become a worldwide public health concern. Although many approaches can be used to achieve short-term weight loss, its maintenance remains a key challenge. Meanwhile, given the same intervention strategies, apparent within-group variability in weight loss and weight regain has been demonstrated. Although the exact reasons for the variability are largely unknown, accumulating evidence has suggested that certain environmental compounds may play an important role in weight gain and obesity development.”

Researchers analyzed data from 621 overweight and obese people who took part in a two-year clinical trial conducted in the mid-2000s. The participants lost an average of 14 pounds in the first six months of the trial, but regained about six pounds over the next 18 months. The people who gained the most weight back had the highest concentration of PFASs, and the link was strongest among women.

“We found that all individual PFASs were significantly associated with more weight regain in women, but not in men, which was in agreement with some previous studies in which the intergenerational effects of PFASs on body weight were observed only in girls but not in boys,” Liu says. “Although the reasons for these gender-specific findings are still unclear, accumulating evidence from experimental research suggests that PFASs are able to interfere with estrogen metabolism and functionalities.”

Although the researchers say more studies are needed to confirm their findings, one thing seems clear.

“These findings suggest that environmental chemicals might play a role in the current obesity epidemic,” the researchers conclude. “Given the persistence of these PFASs in the environment and the human body, their potential adverse effects remain a public health concern.”

The wrappings on fast food often have PFASs in them because the chemicals stop food from sticking. (Photo: Xanya69/Shutterstock)

“This is just another nail to the coffin, so to speak,” study co-author Philippe Grandjean, adjunct professor in the Department of Environmental Health at Harvard T.H. Chan School of Public Health, tells MNN.

“We are decades behind in the research because these compounds were first used in the 1950s and not much toxicology was done and there was no legislation. They were just produced and applied and waste seeped out into the environment.”

Because the chemicals have been used for decades in so many ways, they are very engrained in the environment, Grandjean says. A recent study found that PFAS levels exceed recommendations in the drinking water supplies for at least 6 million Americans.

“Even if we do something about them now, this is a lasting problem and we will continue to be exposed. The greatest concentration is in polar bears and they don’t use sneakers or cookware.”

To reduce your exposure to PFASs, Grandjean suggests calling your municipal water plant to make sure your water doesn’t contain unacceptable levels of these compounds. (Although Grandjean points out that he believes the EPA’s “safe” limit of 70 parts per trillion is too high.) He suggests drinking and cooking with bottled water or installing an activated carbon filter.

When shopping for everything from raingear and waterproof shoes to carpeting and cookware, be informed, Grandjean says. Do research, look for labels and ask if the products have been treated with PFASs.

Cutting back on fast food may also decrease your exposure to the chemicals in the wrappers. (That might also have the added benefit of helping you keep the weight off, too.)